U.S. Department of the Interior

U.S. Geological Survey

Data Series 750

Prepared in cooperation with Trinity Glen Rose Groundwater Conservation District, 

Edwards Aquifer Authority, and San Antonio River Authority

Geodatabase and Characteristics of Springs Within and 

Surrounding the Trinity Aquifer Outcrops in Northern Bexar 

County, Texas, 2010–11
Background, Spring (113) near Leon Creek in the Trinity aquifer outcrop, northern Bexar County, Texas. 

Photograph taken on Tuesday, October 5, 2010. 

Front cover, Spring (104) near the headwaters of Leon Creek in the Trinity aquifer outcrop, northern Bexar 

County, Texas. Photograph taken on Tuesday, October 5, 2010. 

Back cover, Dam with overflow pipe discharging water from spring (109) near Lee Creek in the Trinity 

aquifer outcrop, northern Bexar County, Texas. Photograph taken on Monday, November 15, 2010. 
Geodatabase and Characteristics of 

Springs Within and Surrounding the Trinity 

Aquifer Outcrops in Northern Bexar County, 

Texas, 2010–11

Allan K. Clark, Diana E. Pedraza, Robert R. Morris, and Travis J. Garcia

Prepared in cooperation with Trinity Glen Rose Groundwater Conservation 

District, Edwards Aquifer Authority, and San Antonio River Authority

Data Series 750

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

This and other USGS information products are available at http://store.usgs.gov/

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

To learn about the USGS and its information products visit http://www.usgs.gov/

1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Clark, A.K., Pedraza, D.E., Morris, R.R., and Garcia, T.J., 2013, Geodatabase and characteristics of springs within and 

surrounding the Trinity aquifer outcrops in northern Bexar County, Texas, 2010–11: U.S. Geological Survey Data Series 

750, 20 p. 
iii

Acknowledgments

The authors thank the property owners and property managers in the study area for granting access to springs and the representatives from various Federal, State, and local agencies that 

provided historical data that were invaluable to the study. Special thanks are extended to Bebe 

Fenstermaker, Mary Fenstermaker, LaDona Farinacci, George Hollis, Alan Schuminsky, and 

Ron Hozza for the helpful insights and information they provided.

v

Contents

Abstract ..........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Purpose and Scope .............................................................................................................................1

Description of the Study Area ...........................................................................................................3

Previous Hydrogeologic Investigations ...........................................................................................3

Geologic Framework ...........................................................................................................................3

Hydrogeologic Characteristics ..........................................................................................................3

Methods ..........................................................................................................................................................6

Geodatabase Design ....................................................................................................................................6

Data Input ..............................................................................................................................................6

Data Quality ...........................................................................................................................................7

Metadata ...............................................................................................................................................7

Spring Locations and Characteristics .......................................................................................................7

References Cited ...........................................................................................................................................8

Appendix 1. Geodatabase and Characteristics of Springs ..............................................................11

Figures

1. Map showing springs, streams, and outcrops of the Edwards and Trinity 

aquifers in the study area in northern Bexar County, Texas ................................................2

2. Map showing hydrogeology and faulting of the study area, northern Bexar 

County, Texas ................................................................................................................................4

3. Simplified geodatabase data model for data from springs in the study area in 

northern Bexar County, Texas ...................................................................................................7

Table

1. Hydrogeologic subdivisions/hydrostratigraphic units and characteristics of 

the geologic members of the Edwards and Trinity aquifer outcrops in the study 

area, northern Bexar County, Texas .........................................................................................5
vi

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).
Geodatabase and Characteristics of Springs Within and 

Surrounding the Trinity Aquifer Outcrops in Northern 

Bexar County, Texas, 2010–11

By Allan K. Clark, Diana E. Pedraza, Robert R. Morris, and Travis J. Garcia 

Abstract

The U.S. Geological Survey, in cooperation with the 

Trinity Glen Rose Groundwater Conservation District, the 

Edwards Aquifer Authority, and the San Antonio River 

Authority, developed a geodatabase of springs within and 

surrounding the Trinity aquifer outcrops in a 331-squaremile study area in northern Bexar County, Texas. The data 

used to develop the geodatabase were compiled from 

existing reports and databases, along with spring data 

collected between October 2010 and September 2011. 

Characteristics including the location, discharge, and waterquality properties were collected for known springs and 

documented in the geodatabase. A total of 141 springs were 

located within the study area, and 46 springs were field

verified. The discharge at springs with flow ranged from 

0.003 to 1.46 cubic feet per second. The specific conductance 

of the water discharging from the springs ranged from 167 to 

1,130 microsiemens per centimeter at 25 degrees Celsius with 

a majority of values in the range of 500 microsiemens per 

centimeter at 25 degrees Celsius.

Introduction

The Trinity aquifer is a major source of water for central 

Texas and supplies water for domestic use, livestock use, 

and public supply use (Mace and others, 2000). Although 

considered a major aquifer in Texas (Ashworth and Hopkins, 

1995), springflows from the Trinity aquifer are often much 

smaller compared to springflows from other major aquifers in 

Texas (Mace and others, 2000). Some springs issuing within 

and surrounding the Trinity aquifer outcrops are ephemeral; 

the typically small flows are often lost to evapotranspiration 

within a short distance of discharging to the surface. Of 

the water not lost to evapotranspiration, some will likely 

contribute recharge to the Edwards aquifer downgradient 

(Ashworth and Hopkins, 1995) (fig. 1).

Between 2000 and 2011, the population of Bexar County, 

Tex., increased 25.6 percent, whereas the population of Texas 

increased 22.6 percent and the population of the United States 

increased only 10.4 percent (U.S. Census Bureau, 2009, 2010, 

2011). In Bexar County, this population growth has resulted 

in an increased demand for water from the Trinity aquifer. 

Additionally there are two military facilities in the study area 

that withdraw water from the Trinity aquifer. The effect of 

increased withdrawals from the Trinity aquifer on springflow 

has not been documented; however, the decreased storage 

in the Trinity aquifer as a result of drought and increased 

pumping has been noted in previous studies (Mace and others, 

2000). Therefore, it is important to document the location, 

current discharge, and basic water-quality information 

of springs that may discharge from the Trinity aquifer in 

northern Bexar County to provide a baseline for future 

conditions. Accordingly, the U.S. Geological Survey (USGS), 

in cooperation with the Trinity Glen Rose Groundwater 

Conservation District, the Edwards Aquifer Authority, and 

the San Antonio River Authority, developed a geodatabase 

to document springs within and surrounding the upper and 

middle Trinity aquifer outcrops in northern Bexar County. 

Information pertaining to the springs in the study area was 

compiled from various Federal, State, and local agencies and 

entered into a geodatabase. 

Purpose and Scope

The purpose of this report is to provide information on 

the compilation of geologic and hydrogeologic information 

pertaining to selected springs within and surrounding the 

Trinity aquifer outcrops in northern Bexar County. Detailed 

information for 141 springs in the study area were compiled 

from existing reports and databases, as well as from data 

collected onsite that include the location, discharge, and 

water-quality characteristics of selected springs. The focus of 

the geodatabase is the springs; however, existing information 

regarding hydrogeology, faulting, soils, and streams is also 

included in the geodatabase. All of the information that was 

compiled pertaining to the Trinity aquifer is for the upper 

and middle Trinity aquifers; no information was compiled 

pertaining to the lower Trinity aquifer.
San Antonio

29°45'

29°40'

29°35'

98°32'

98°40'

98°48'

See 

inset

MEDINA COUNTY

BEXAR COUNTY

COMAL COUNTY

BANDERA 

COUNTY

KENDALL 

COUNTY

Chimenea Creek

Elm Cree k

West E ml Creek

East Elm Cree k

Cibolo Creek

Balcones Creek

Rundale Creek

Meusebach Creek

Elm

Waterhole Creek

Mud Creek

Helotes Creek

French Creek

Panther Springs Creek

Olmos Creek

Los Reyes Creek

Leon Creek

Pecan Creek

Helotes Creek

Cibolo Creek

Creek

Creek

Mud

Mustang

Creek

Creek

Creek

Lewis 

Fo

Huesta Lee Creek

Clear 

Creek

Culebra 

Leon

Leon

Salado 

Salado 

Creek

Creek

Creek

59

66

6

69 68

70

71 73

7

78

77

79

80

82 85

83 84

8

86

88

87

90

89

92

94 93 9

9695

98

99

100

97

101

91

102

103

105 104 106

107

109

110

111

112

113

114

115

116

118

119

120

121

12

125

126

127

128

12

130

132

13

133

135

14

139 138

141

16 17 15

137

18

2

20

19

75 74 76

21 22 67,23

24

26

47

27

28

3

1

30

31

33

32

35 34

36

37

4

40

38

39

41

42

45

49 48 50

51

140 52

54

53 43 25

44

5

117136

1

108

81

¬«1604

§ ̈¦10

§ ̈¦10

£¤281

£¤281

EXPLANATION

Upper Trinity aquifer outcropMiddle Trinity aquifer outcropEdwards aquifer outcropEphemeral streamPerennial streamStudy boundarySpring with map identifier—Tail  points in direction of flow; appendix 1

105

BEXAR COUNTY

Study area

BALCONES FAULT ZONE

BALCONES FA

ZONE

Physiographic pr

Fenneman and J

Base modified from U.S. Geological Survey 1:100,000-scale digital data Universal Transverse Mercator Projection, zone 14North American Datum of 1983

Aquifer divisions modified from Clark and others, 2009,

and Stein and Ozuna, 1995

0 2.5 5 MILES0 2.5 5 KILOMETERS

Figure 1. Springs, streams, and outcrops of the Edwards and Trinity aquifers in the study area in northern Bexar County, Texas.
Introduction 3

Description of the Study Area

The study area encompasses 331 square miles in northern 

Bexar County coincident with the outcrops of the Edwards 

and Trinity aquifers within Bexar County (fig. 1). The study 

area has been characterized in previous reports such as 

Stein and Ozuna (1995) and Clark and others (2009), which 

concentrated on the hydrogeology of the Edwards and Trinity 

aquifer outcrops, respectively. The predominant soils within 

the study area are shallow (U.S. Department of Agriculture, 

1991), and there are few agricultural activities (mostly the 

growing of grass and feed crops in stream valleys) (Ashworth, 

1983). The study area is within the Balcones fault zone, 

which is the transition between the Edwards Plateau section 

of the Great Plains physiographic province and the Coastal 

Plain physiographic province (Fenneman and Johnson, 1946) 

(fig. 1). Land surface elevations range from 769 to 1,898 

feet (ft) above the North American Vertical Datum of 1988; 

the maximum relief is approximately 1,100 ft. A subtropical, 

subhumid climate prevails in the study area, which is 

characterized by hot summers and mild winters (Larkin and 

Bomar, 1983). The average annual rainfall is approximately 

32.27 inches (in.) (National Oceanic and Atmospheric 

Administration, 2011).

Previous Hydrogeologic Investigations

Lozo and Smith (1964) established the nomenclature of 

the Trinity Group, and Ashworth (1983) subdivided the Trinity 

aquifer into the upper Trinity, middle Trinity, and lower Trinity 

aquifers. As part of the regional aquifer-system analysis of the 

Edwards and Trinity aquifer system, Barker and others (1994) 

described the hydrogeologic framework of the aquifers. Brune 

(1975) compiled the locations and discharge information of 

281 springs in Texas. Brune (1981) included a description of 

springs in 183 of the 254 counties in Texas, with discharge 

data and anecdotes about the springs from the 15th century 

to the early 1980s. Heitmuller and Reece (2003) created a 

database of historically documented springs and discharge 

measurements in Texas; their database included information 

on 1,891 springs and a total of 6,924 discharge measurements. 

Heitmuller and Williams (2006) created a database of 

historical water-quality data for selected springs in Texas 

by ecoregion; their database combined previously compiled 

and published water-quality data from various sources and 

documented the compilation of water-quality data for 232 

springs in Texas.

Geologic Framework

The study area contains outcrops of the Edwards and 

Trinity Groups (fig. 2, table 1). The Glen Rose Limestone 

(fig. 2, table 1) of the Trinity Group consists of beds of 

moderately resistant, massive, chalky limestone that alternate 

with beds of less resistant, clay-rich limestone (Livingston 

and others, 1936). Ashworth (1983) stated that the Glen 

Rose Limestone is approximately 721–770 ft thick in the 

San Antonio, Tex., area; Clark (2003, 2005) documented 

thicknesses ranging from 715 to 810 ft (table 1). George 

(1952) informally separated the Glen Rose Limestone into 

upper and lower members (fig. 2, table 1) on the basis of 

the presence of a thin, regionally extensive bed containing 

an abundance of the small pelecypod Corbula martinae. 

Perkins (1974) stated that the lower member of the Glen Rose 

Limestone is composed of limestone, dolostone, and dolomitic 

limestone. The upper member of the Glen Rose Limestone 

consists of a layer of 10–20 ft of partially to mostly dissolved 

evaporites composed of highly altered crystalline limestone 

and chalky mudstone overlain by 135–180 ft of alternating 

wackestone, packstone, and mudstone. Overlying this is 

10–20 ft of dissolved evaporites and carbonate rock with 

collapse structures, which in turn is overlain by 240–270 ft of 

alternating and interfingering mudstone, marl, wackestone, 

and packstone with local evaporites (table 1).

The Kainer Formation (fig. 2, table 1) of the Edwards 

Group consists of fossiliferous mudstone and wackestone that 

grade upward into dolomitic mudstone with evaporites and 

terminates in a miliolid grainstone (Stein and Ozuna, 1995). 

The basal nodular member (fig. 2, table 1) of the Kainer 

Formation is a shaly, nodular limestone: burrowed mudstone 

to wackestone (Stein and Ozuna, 1995). The basal nodular is 

approximately 50–60 ft thick in the study area.

All of these units are highly faulted by the Balcones 

fault zone (fig. 1), a tensional zone that is approximately 

20 miles wide with numerous high-angle, mostly normal, 

subparallel faults that are dropped down in an en echelon 

(stairstep) pattern to the southeast, toward the Gulf of 

Mexico (George, 1952; fig. 1). These faults often displace 

stratigraphically younger rocks against older ones. Total 

vertical displacement across Bexar County is more than 3,400 

ft (Maclay, 1995), and the combined displacement of the faults 

in the study area varies from approximately 1,200 ft in the 

east to approximately 1,400 ft in the west; in the study area, 

displacement on faults ranges from tens of feet to several 

hundred feet (Small, 1986; Clark and others, 2009). 

Hydrogeologic Characteristics

The formations of the Trinity Group compose the 

Trinity aquifer (fig. 2). The upper member of the Glen Rose 

Limestone composes the upper Trinity aquifer (Ashworth, 

1983; table 1). The upper Trinity aquifer is a relatively 

impermeable hydrogeologic unit that restricts infiltration of 

surface water and groundwater flow (Ashworth, 1983; Clark 

and others, 2009). Clark (2003, 2005) subdivided the upper 

Trinity aquifer into five mappable units (A–E). Clark and 

others (2009) extended the five earlier hydrostratigraphic 

unis (Clark 2003, 2005) through northern Bexar County 

and informally renamed the units from top to bottom 

as the “cavernous,” “Camp Bullis,” “upper evaporite,” 

“fossiliferous,” and “lower evaporite” hydrostratigraphic 
Helotes Creek

59

66

6

69 68

70

71 73

7

78

77

79

80

82 85

83 84

8

86

88

87

90

89

92

94 93 9

9695

98

99

100

97

101

91

102

103

105 104 106

107

109

110

111

112

113

114

115

116

118

119

120

121

12

125

126

127

128

12

13

132

13

133

135

14

139 138

141

16 17 15

137 18

2

20

19

75 74 76

21 22 67,23

24

26

47

27

28

3

1

30

31

33

32

35 34

36

37

4

4038

39

41

42

45

49 48

50

51

140 52

54

53 43 25

44

5

117136

1

108

81

Chimenea Creek

MEDINA COUNTY

BEXAR COUNTY

COMAL COUNTY

BANDERA 

COUNTY

KENDALL 

COUNTY

Creek

Creek

Mud

Mustang

Creek

Creek

Cibolo Creek

Creek

Lewis 

Fo

Huesta Lee Creek

Clear 

Creek

Culebra 

Leon

Leon

Salado 

Salado 

Creek

Creek

Creek

Kgrcb

Kgrcb

Kgrue

Kgrf

Kgrf

Kgrue

Kgrcb

Kgrcb

Kgrl

Kgrl

Kgrl

Kgrc

Kgrc

Kgrc

Kkbn

Kkbn

Elm Cree k

West E ml Creek

East Elm Cree k

Cibolo Creek

Balcones Creek

Rundale Creek

Meusebach Creek

Elm

Waterhole Creek

Mud Creek

Helotes Creek

French Creek

Panther Springs Creek

Olmos Creek

Los Reyes Creek

Leon Creek

Pecan Creek

29°45'

29°40'

29°35'

98°32'

98°40'

98°48'

See 

inset

Edwards 

Edwards

aquifer

Trinity

Lower 

Basal 

nodular

Upper 

Aquifer Group Formation Member

Upper Trinity aquifer

Middle 

Trinity

aquifer

Glen Rose Limestone Kainer

EXPLANATION

Kkbn

Kgrc

Kgrcb

Kgrue

Kgrf

Kgrle

Kgrl

Hydrogeologic subdivision Member younger than hydrogeolog subdivision VIII VIIIInformal hydrostratigraphic uni Cavernous Camp Bullis Upper evaporite Fossiliferous Lower evaporite Not subdivided

Lewis 

Creek

60

61

62

63

64 65 46

55

56, 57

58

Kgrcb

Kgrue

Kgrf

Base modified from U.S. Geological Survey 1:100,000-scale digital data Universal Transverse Mercator Projection, zone 14North American Datum of 1983

Hydrogeolog

0 2.5 5 MILES0 2.5 5 KILOMETERS

Figure 2. Hydrogeology and faulting of the study area, northern Bexar County, Texas.
Introduction 5

Table 1. Hydrogeologic subdivisions/hydrostratigraphic units and characteristics of the geologic members of the Edwards and Trinity 

aquifer outcrops in the study area, northern Bexar County, Texas. 

[*, not exposed in the study area; --, not subdivided]

Group1 Formation1 Member1 Thickness 

(feet)2 Lithology Aquifer3

Informal 

hydrostratigraphic 

unit4

(formal 

hydrogeologic 

subdivision where 

shaded)5

Number of 

springs6

Edwards Kainer Basal 

nodular

50–60 Shaly, nodular limestone: burrowed 

mudstone and miliolid grainstone (Stein 

and Ozuna, 1995)

Edwards VIII 8

Trinity

Glen Rose 

Limestone

Upper

120 Alternating and interfingering mudstone, 

wackestone, and packstone with local 

evaporites (Clark and others, 2009)

Trinity

Upper Trinity

Cavernous (interval 

A of Clark, 2003, 

2005)

27

120–150 Alternating and interfingering mudstone, 

marl, wackestone, and packstone (Clark 

and others, 2009)

Camp Bullis (interval 

B of Clark, 2003, 

2005)

42

10–20 Dissolved evaporites and carbonate rock 

with collapsed structures; areas of 

recrystallized limestone (Clark and 

others, 2009)

Upper evaporite 

(interval C of 

Clark, 2003, 2005)

19

135–180 Alternating wackestone, packstone, 

and mudstone; common Orbitolina 

minutia (Romer); massive boundstone 

(biostrome) near top of subdivision 

(Clark and others, 2009)

Fossiliferous (interval 

D of Clark, 2003, 

2005)

33

10–20 Partially to mostly dissolved sequence 

of evaporites consisting of highly 

altered crystalline limestone and chalky 

mudstone; corbula bed (Clark and 

others, 2009)

Lower evaporite 

(interval E of 

Clark, 2003, 2005)

1

Lower 320 Limestone, dolostone, and dolomitic 

limestone; diverse mollusk assemblages 

and locally rudist reefs (Perkins, 1974)

Middle Trinity

-- 11

Bexar Shale -- 60–70 * -- *

Cow Creek 

Limestone

-- 50–70 * -- *

1

Modified from Forgotson (1956), Rose (1972), and Ashworth (1983).

2

From Maclay (1995), Barker and Ardis (1996), Clark (2003, 2005), and Clark and others (2009).

3

Modified from Stein and Ozuna (1995), Clark (2003, 2005), and Clark and others (2009).

4

Modified from Clark (2003, 2005) and Clark and others (2009).

5

From Maclay and Small (1986).

6

Springs identified by the hydrogeologic subdivision where the spring is located.
6 Geodatabase and Characteristics of Springs Within and Surrounding the Trinity Aquifer Outcrops, 2010–11

units (fig. 2, table 1). The lower member of the Glen Rose 

Limestone, along with the underlying Bexar Shale and 

Cow Creek Limestone, compose the middle Trinity aquifer 

(Ashworth, 1983; table 1). The hydrogeologic units that 

compose the lower Trinity aquifer are not found at the surface 

in the study area (Perkins, 1974; Clark and others, 2009). 

In the study area in northern Bexar County, Veni (1994) 

and Clark (2003) observed that the upper Trinity aquifer 

exhibits greater porosity and more permeability in its outcrops 

and shallow subcrops than is typically observed in the upper 

Trinity aquifer outside of northern Bexar County. Compared to 

the Edwards aquifer, the Trinity aquifer generally has higher 

hydraulic heads (Ashworth, 1983), lower porosity, and lower 

primary permeability (Clark, 2003). Because of its relatively 

low primary permeability, most recharge entering the outcrop 

of the Trinity aquifer enters through dissolution channels that 

range in size from minute openings to large caverns, some of 

which can take in large quantities of water (Livingston and 

others, 1936) (table 1). 

Faults are an important hydrogeologic feature in the 

Edwards and Trinity aquifers in the study area. According to 

George (1952), some faults may act as barriers to groundwater 

flow and result in water being deflected parallel to the strike 

of the fault. George (1952) observed water-level and waterquality differences on opposite sides of faults that juxtaposed 

the younger Edwards aquifer against the older Trinity aquifer. 

Methods

A field reconnaissance of springs in the study area was 

done between October 2010 and September 2011 to verify 

the existing data and collect additional data pertaining to the 

springs (discharge measurements, water-quality data, property 

owner and photographic documentation). A total of 46 of 

the 141 springs (fig. 1, app. 1) were visited during the field 

reconnaissance.

Location data were collected by using a hand-held Global 

Positioning System (GPS) unit or a digital camera with an 

integrated GPS unit, both with horizontal accuracy of tens 

of feet. After a spring was verified, it was assigned a USGS 

station number based on its location. The hydrostratigraphic 

unit outcropping at each spring was determined by overlaying 

existing hydrogeologic maps with the point information 

(latitude and longitude) obtained for each spring. The 

discharge measurements of springflow were made according 

to USGS methods detailed in Sauer and Turnipseed (2010) 

and Rantz and others (1982) by using a rod-mounted 

FlowTracker (Acoustic Doppler Velocimeter [ADV]) (Xylem 

Analytics, 2012a). A number of the springs could not be 

measured at the orifice for reasons such as inundation of the 

discharge location, the presence of multiple small orifices, 

or a channel that was either too shallow or too narrow 

to accommodate the measuring equipment. In situations 

where a direct measurement made by using the ADV was 

not possible, the springflow was estimated by measuring 

the time required to fill a container of known volume three 

times and then using the average to compute the springflow 

rate. Where the physical setting of the spring did not allow 

for the filling of a known volume, the amount of flow was 

approximated by making rudimentary estimates of the depth, 

width, and velocity. The specific conductance of springflow 

was measured in-place by using methods described by Radtke 

and others (2005). Specific-conductance measurements were 

made by using a YSI 6920 V2 multiparameter water-quality 

instrument (sonde) (Xylem Analytics, 2012b).

Geodatabase Design

A geodatabase contains spatial and tabular data and 

allows users to associate tabular data with physical and spatial 

components. By providing a framework to organize and 

understand data attributes such as the geographic location 

and water-quality characteristics, geographically referenced 

data can be manipulated to produce maps, make queries, and 

perform other types of spatial analyses. The geodatabase for 

this study was developed by using the Environmental Systems 

Research Institute (ESRI) geographic information system 

(GIS) software (ArcGIS) (Environmental Systems Research 

Institute, Inc., 2008; Zeiler, 1999). A geodatabase includes 

spatial layers of data, called feature classes, which represent 

the various types of vector geometry such as points, lines, and 

polygons. These data are referenced to a specific location and 

related to one another thematically within the geodatabase. 

In the geodatabase for the study area, a point feature class 

is used to represent the location for each spring. Additional 

detailed information about each feature is stored in an attribute 

table linked to the point feature class to form a relationship 

class. Relationship classes are created to connect data from 

the information table to the geographic feature class by using 

unique identifiers (app. 1). 

A preliminary geodatabase was first developed to 

store all of the data for this study. Revisions were made to 

the geodatabase to reflect changes resulting from onsite 

verification of existing spring-related data and to add 

discharge and water-quality data collected during 2010–11. 

The geodatabase developed for this study provides an accurate 

spatial representation of the springs within and surrounding 

the upper and middle Trinity aquifer outcrops in the study 

area. A simplified schematic depicts data sources, the feature 

class (springs), and attribute tables, which contain the 

information pertaining to the study area (fig. 3).

Data Input

Historical data were formatted as needed and imported 

into the geodatabase. This information was used to populate 

the spring data table (app. 1). Field-verified springs were 

assigned a USGS station number derived from the latitude 

and longitude. Unique identifiers were assigned to all springs 
Geodatabase Design 7

for use in the spring feature class. The fields populated in 

the spring data table (app. 1) include the map identifier, 

unique identifier, USGS station number (if applicable), name 

of spring (if known), source of the spring name, longitude 

and latitude in decimal degrees, field verified, specific 

conductance, discharge, field visit date, hydrostratigraphic 

unit at surface, and soil type at surface. Relationships between 

spring feature classes and attribute tables were created by 

using the unique identifier. The unique identifier is common 

to the spring feature class and attribute tables and was used to 

build the relationship class (Zeiler, 1999). 

Data Quality

All springs were tentatively identified according to 

the surficial expression of the aquifer where the spring was 

located. At 26 of the springs, no discharge was evident 

(app. 1); the property owners of where these 26 springs were 

located indicated that these springs had been flowing until 

the beginning of the current (2010–12) drought. Property 

access and time constraints prohibited the verification of the 

remaining springs. When onsite verification was not possible, 

springs were identified from previously published data. 

Quality-assurance methods of database querying were applied 

to identify duplicate records. Duplicate names accounted 

for most of the errors. A few springs were visited more than 

once, and data from different visits were sometimes initially 

entered into the database with slightly different coordinates. 

Upon verification of duplicate springs, the multiple sets 

of information were combined into a single spring record. 

Because of different field visit dates, four springs have two 

record entries, one for each field visit date; all other springs 

have only one field visit date (app. 1). 

Metadata

Metadata for the information input to the geodatabase 

were written by using Federal Geographic Data Committee 

(FGDC) standards (Federal Geographic Data Committee, 

2009). The metadata include source information (title, 

abstract, publication date, and author) and geographic 

elements (geographic extent, projection information, and 

database elements such as attribute label definitions). The 

metadata were reviewed by using the Geospatial Metadata 

Validation Service (Schweitzer, 2003) and internal USGS 

personnel. 

Spring Locations and Characteristics 

Information pertaining to spring locations and 

characteristics were obtained from published reports, USGS 

1:24,000-scale topographic maps, and available digital 

databases of springs. Data from existing USGS reports 

(Heitmuller and Reece, 2003; Heitmuller and Williams, 2006; 

Clark and others, 2009), Camp Bullis Joint Training Facility, 

Camp Stanley Storage Activity, and private property owners 

were included. Existing data regarding digital elevation 

USGS

CSSA

CBJTF

Spring

Spring data

Field data

Soils and hydrogeology

U.S. Geological Survey

Camp Stanley Storage 

Activity 

Camp Bullis Joint

Training Facility 

Simplified data model elements

 Data source—Digital or hardcopy data used in the

 geodatabase compilation

 Geodatabase feature class—Spatial data features 

 stored as points, lines, or polygons

 Geodatabase attribute table—Data stored in rows

 and columns, generally related to a feature class

 Geodatabase relationship class—Links spatial

 and tabular data

Data source

 Digital 

Geodatabase

 Point feature class 

 Attribute table

 Relationship class

 

EXPLANATION

Figure 3. Simplified geodatabase data model for data from springs in the study area in northern Bexar County, Texas.
8 Geodatabase and Characteristics of Springs Within and Surrounding the Trinity Aquifer Outcrops, 2010–11

models, hydrogeology, and soils were also included in the 

geodatabase. Discharge and specific conductance collected 

during the field reconnaissance in 2010 and 2011were 

integrated into the geodatabase. 

A total of 141 springs were located within the study 

area, and 46 springs were field verified. The discharge at 

springs with flow ranged from 0.003 to 1.46 cubic feet per 

second. Most of the springs with identified discharge were 

found where the upper and middle parts of the Trinity aquifer 

outcrop. During field reconnaissance, eight springs were 

identified that discharge near the base of the Edwards aquifer 

outcrop. The gradational nature of the contact between the 

Edwards and Trinity Groups made the exact location of 

the lithologic change difficult to determine. Furthermore, 

because of the steep terrain where these springs were located, 

the contact between the Edwards and Trinity Groups was 

sometimes indistinct. These springs were tentatively identified 

as issuing from hydrogeologic subdivision VIII of the 

Edwards aquifer and were included in the geodatabase because 

of their proximity to the upper part of the Trinity aquifer 

outcrop. Detailed water-quality analyses that were beyond the 

scope of this study could be done to determine if the water 

issuing from most of the springs is consistent with water found 

in the Trinity or Edwards aquifers or if it represents a blend of 

water from both aquifers.

The specific hydrogeologic or Trinity aquifer unit 

identified at surface where each spring was located is listed 

in table 1 and appendix 1. Specific conductance was measured 

in 21 springs and ranged from 167 to 1,130 microsiemens 

per centimeter at 25 degrees Celsius (μS/cm at 25 °C). 

There were nine springs that measured between 600 and 

1,130 μS/cm at 25 °C. Of these, one was tentatively identified 

as issuing from hydrogeologic subdivision VIII of the 

Edwards aquifer, three from the cavernous hydrostratigraphic 

unit of the upper Trinity aquifer, one from the Camp Bullis 

hydrostratigraphic unit of the upper Trinity aquifer, two 

from the fossiliferous hydrostratigraphic unit of the upper 

Trinity aquifer, and two from the middle Trinity aquifer 

(fig. 2, table 1). Of the springs with a specific conductance 

less than 600 μS/cm at 25 °C, one was tentatively identified 

as issuing from the hydrogeologic subdivision VIII of the 

Edwards aquifer, three from the cavernous hydrostratigraphic 

unit of the upper Trinity aquifer, two from the Camp Bullis 

hydrostratigraphic unit of the upper Trinity aquifer, one 

from the fossiliferous hydrostratigraphic unit of the upper 

Trinity aquifer, and four from the middle Trinity aquifer 

(fig. 2, table 1). Follow-up studies to qualify the geochemical 

characteristics of the springs are needed; geochemical 

investigations including detailed water-quality analyses would 

help to confirm the aquifer or combination of aquifers that 

supply flow to each spring.

Soils were included in the geodatabase because of 

the relationship between soil type and underlying geology; 

changes in soil type might aid in the determination of the 

hydrostratigraphic unit that springs are issuing from if 

bedrock is not evident. In the Natural Resources Conservation 

Service (2012) data, the type of soil is related to the percent 

slope, so the soil data are presented with percent slope in 

the geodatabase. The soil and slope data may aid in further 

analyses that use the geodatabase. 

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history and hydrogeologic setting of the Edwards-Trinity 

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of Comal County, Texas: U.S. Geological Survey WaterSupply Paper 1138, 126 p.

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measurements in Texas: U.S. Geological Survey Open File 

Report 03–315, 4 p., accessed May 7, 2010, at http://pubs.

usgs.gov/of/2003/ofr03-315/.

Heitmuller, F.T., and Williams, I.P., 2006, Compilation of 

historical water-quality data for selected springs in Texas, 

by ecoregion: U.S. Geological Survey Data Series 230, 

32 p.

Larkin, T.J., and Bomar, G.W., 1983, Climatic atlas of Texas: 

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resources of the Edwards Limestone in the San Antonio 

area, Texas: U.S. Geological Survey Water-Supply Paper 

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Mace, R.E., Chowdhury, A.H., Anaya, R., and Way, S.C., 

2000, Groundwater availability of the Trinity aquifer, Hill 

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aquifer in the San Antonio area, Texas: U.S. Geological 

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64 p.

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hydrology of the Edwards aquifer in the San Antonio area, 

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the Comanche Cretaceous Glen Rose Limestone of central 

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book 9, chap. A6., section 6.3, accessed December 5, 2012, 

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discharge: U.S. Geological Survey Water-Supply Paper 

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at gaging stations: U.S. Geological Survey Techniques and 

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10 Geodatabase and Characteristics of Springs Within and Surrounding the Trinity Aquifer Outcrops, 2010–11

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Appendix 1—Geodatabase and Characteristics of Springs 

Within and Surrounding the Upper and Middle Trinity Aquifer 

Outcrops in Northern Bexar County, Texas, 2010–11

Appendix 1

Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CouContinued[USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/y

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer]

Map 

identifier Unique identifier USGS station number Name of spring

Source 

of 

spring 

name

Longitude 

(dd)

Latitude 

(dd)

Field 

verified

Specific 

conductance 

(μS/cm at 

25 °C)

Discharge 

(ft3/s)

Field 

visit date (MM/DD/

YY)

Field 

observation 

at land 

surface

1 SPNG_1 -- Unnamed -- -98.7614 29.6535 No nm nm -- Cavernous Brack

to 

2 SPNG_2 -- Pastora 

Spring

GNIS -98.78 29.6072 No nm nm -- Cavernous Brack

to 

3 SPNG_3 -- Unnamed -- -98.6991 29.6136 No nm nm -- Cavernous Eckra

per

4 SPNG_4 -- Unnamed -- -98.6748 29.6174 No nm nm -- Camp Bullis Brack

to 

5 SPNG_5 293830098442601 Morales 

Spring

GNIS -98.7406 29.6417 Yes nm nm -- Camp Bullis Brack

to 

6 SPNG_6 -- Unnamed -- -98.7203 29.6419 No nm nm -- Camp Bullis Krum 

7 SPNG_7 -- Unnamed -- -98.6534 29.6489 No nm nm -- Cavernous Krum 

8 SPNG_8 -- Unnamed -- -98.7158 29.6537 No nm nm -- Cavernous Krum 9 SPNG_9 -- Unnamed -- -98.6562 29.6605 No nm nm -- Fossiliferous Krum 

10 SPNG_10 -- Unnamed -- -98.6373 29.6629 No nm nm -- Cavernous Lewi

per

11 SPNG_11 294023098233901 Devine 

Spring

GNIS -98.3943 29.6731 Yes 570 0.003 10/15/10 Cavernous Eckra

15 

12 SPNG_12 -- Unnamed -- -98.4651 29.6739 No nm nm -- VIII1 Eckra

per

13 SPNG_13 -- Hamilton 

Spring

GNIS -98.797 29.6769 No nm nm -- Fossiliferous Eckra

per

14 SPNG_14 -- Indian 

Springs

GNIS -98.4076 29.687 No nm nm -- VIII1 Eckra

15 

15 SPNG_15 -- Unnamed -- -98.5292 29.6899 No nm nm -- Upper 

evaporite

Krum 

16 SPNG_16 -- Jack 

Mountain Spring

GNIS -98.7961 29.6908 No nm nm -- Upper 

evaporite

Brack

to 

17 SPNG_17 294125098314602 6820611 TWDB -98.5298 29.6904 Yes nm 0 05/14/12 Upper 

evaporite

Krum 

18 SPNG_18 -- Wolf Head 

Spring

GNIS -98.7695 29.6927 No nm nm -- Camp Bullis Eckra

15 

Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar Co[USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer]
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CoContinued [USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer] Map identi- fier Unique identifier USGS station number Name of spring Source of spring name Longitude (dd) Latitude (dd) Field verified Specific conduc- tance (μS/cm at 25 °C) Dis- charge (ft3/s) Field visit date (MM/DD/ YY) Field observation at land surface 

19 SPNG_19 -- Unnamed -- -98.5261 29.6938 No nm nm -- Upper evaporite Krum 20 SPNG_20 -- Unnamed -- -98.5263 29.6941 No nm nm -- Camp Bullis Krum 21 SPNG_21 -- Unnamed -- -98.7802 29.7051 No nm nm -- Cavernous Brack

20 

22 SPNG_22 -- Unnamed -- -98.7424 29.7113 No nm nm -- Fossiliferous Krum 23 SPNG_23 -- Unnamed -- -98.5575 29.7152 No nm nm -- Fossiliferous Krum 24 SPNG_24 -- Unnamed -- -98.4223 29.7204 No nm nm -- Upper evaporite Eckra

pe

25 SPNG_25 -- Unnamed -- -98.5699 29.7128 No nm nm -- Camp Bullis Brack

12 

26 SPNG_26 -- Unnamed -- -98.5766 29.7218 No nm nm -- Fossiliferous Krum 27 SPNG_27 294037098342101 6820510 TWDB -98.5725 29.677 Yes 617 0 05/14/12 Fossiliferous Krum 

28 SPNG_28 -- Unnamed -- -98.739 29.6349 No nm nm -- Camp Bullis Brack

to 

29 SPNG_29 -- Unnamed -- -98.3969 29.6961 No nm nm -- VIII1 Eckra

15 

30 SPNG_30 -- Unnamed -- -98.7146 29.6408 No nm nm -- Upper evaporite Krum 

31 SPNG_31 -- Unnamed -- -98.6007 29.7409 No nm nm -- Middle Trinity Oaka

slo

32 SPNG_32 -- Unnamed -- -98.5589 29.7502 No nm nm -- Middle Trinity Tarpl

33 SPNG_33 -- Unnamed -- -98.559 29.7515 No nm nm -- Middle Trinity Orif 

fre

34 SPNG_34 -- Unnamed -- -98.5742 29.7293 No nm nm -- Fossiliferous Eckra

pe

35 SPNG_35 -- Unnamed -- -98.5777 29.7301 No nm nm -- Lower 

evaporite

Krum 

36 SPNG_36 -- Unnamed -- -98.5672 29.7374 No nm nm -- Fossiliferous Anha

37 SPNG_37 294509098325801 6812802 TWDB -98.5494 29.7524 Yes nm 0 05/14/12 Middle 

Trinity

Eckra

pe

38 SPNG_38 -- Unnamed -- -98.5916 29.7161 No nm nm -- Camp Bullis Brack

12 
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CouContinued[USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/y

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer]

Map 

identifier Unique identifier USGS station number Name of spring

Source 

of 

spring 

name

Longitude 

(dd)

Latitude 

(dd)

Field 

verified

Specific 

conductance 

(μS/cm at 

25 °C)

Discharge 

(ft3/s)

Field 

visit date (MM/DD/

YY)

Field 

observation 

at land 

surface

39 SPNG_39 -- Unnamed -- -98.5807 29.7199 No nm nm -- Upper 

evaporite

Brack

12 

40 SPNG_40 -- Unnamed -- -98.5917 29.7158 No nm nm -- Camp Bullis Brack

12 

41 SPNG_41 -- Unnamed -- -98.5882 29.7035 No nm nm -- Fossiliferous Krum 42 SPNG_42 -- Unnamed -- -98.582 29.6987 No nm nm -- Fossiliferous Brack

12 

43 SPNG_43 -- Unnamed -- -98.5748 29.7126 No nm nm -- Camp Bullis Brack

12 

44 SPNG_44 -- Unnamed -- -98.5748 29.7124 No nm nm -- Upper 

evaporite

Brack

12 

45 SPNG_45 -- Unnamed -- -98.5791 29.6876 No nm nm -- Camp Bullis Brack

12 

46 SPNG_46 -- Unnamed -- -98.5739 29.6842 No nm nm -- Fossiliferous Brack

12 

47 SPNG_47 -- Unnamed -- -98.5767 29.722 No nm nm -- Fossiliferous Krum 48 SPNG_48 -- Unnamed -- -98.5736 29.7242 No nm nm -- Fossiliferous Brack

12 

49 SPNG_49 -- Unnamed -- -98.5707 29.7266 No nm nm -- Upper 

evaporite

Brack

12 

50 SPNG_50 -- Unnamed -- -98.5624 29.7185 No nm nm -- Camp Bullis Brack

12 

51 SPNG_51 -- Unnamed -- -98.5706 29.7018 No nm nm -- Upper 

evaporite

Krum 

52 SPNG_52 -- Unnamed -- -98.5634 29.7007 No nm nm -- Camp Bullis Krum 53 SPNG_53 -- Unnamed -- -98.5705 29.7119 No nm nm -- Upper 

evaporite

Krum 

54 SPNG_54 -- Unnamed -- -98.5705 29.7115 No nm nm -- Upper 

evaporite

Krum 

55 SPNG_55 294058098342401 6820515 TWDB -98.5734 29.6827 Yes nm 0 05/14/12 Fossiliferous Krum 

56 SPNG_56 294058098342402 6820516 TWDB -98.5734 29.6828 Yes nm 0 05/14/12 Fossiliferous Krum 

57 SPNG_57 294058098342403 6820517 TWDB -98.5734 29.6828 Yes nm 0 05/14/12 Fossiliferous Krum 

58 SPNG_58 -- Unnamed -- -98.5651 29.6836 No nm nm -- Camp Bullis Brack

12 
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CoContinued [USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer] Map identi- fier Unique identifier USGS station number Name of spring Source of spring name Longitude (dd) Latitude (dd) Field verified Specific conduc- tance (μS/cm at 25 °C) Dis- charge (ft3/s) Field visit date (MM/DD/ YY) Field observation at land surface 

59 SPNG_59 -- Unnamed -- -98.5596 29.691 No nm nm -- Camp Bullis Brack

20 

60 SPNG_60 -- Unnamed -- -98.5645 29.6843 No nm nm -- Camp Bullis Brack

12 

61 SPNG_61 -- Unnamed -- -98.5679 29.6885 No nm nm -- Camp Bullis Brack

12 

62 SPNG_62 -- Unnamed -- -98.5682 29.6883 No nm nm -- Upper evaporite Krum 63 SPNG_63 -- Unnamed -- -98.5673 29.6894 No nm nm -- Camp Bullis Eckra

pe

64 SPNG_64 -- Unnamed -- -98.5715 29.6841 No nm nm -- Fossiliferous Krum 

65 SPNG_65 294102098341801 6820518 TWDB -98.5717 29.6838 Yes nm 0 -- Fossiliferous Krum 

66 SPNG_66 -- Unnamed -- -98.5496 29.7229 No nm nm -- Fossiliferous Eckra

pe

67 SPNG_67 -- Unnamed -- -98.5575 29.7153 No nm nm -- Fossiliferous Krum 68 SPNG_68 -- Unnamed -- -98.5521 29.7008 No nm nm -- Camp Bullis Brack

20 

69 SPNG_69 -- Unnamed -- -98.5504 29.7015 No nm nm -- Camp Bullis Eckra

pe

70 SPNG_70 -- Unnamed -- -98.5472 29.706 No nm nm -- Camp Bullis Eckra

pe

71 SPNG_71 -- Unnamed -- -98.5387 29.7024 No nm nm -- Camp Bullis Brack

20 

72 SPNG_72 -- Unnamed -- -98.5462 29.6887 No nm nm -- Camp Bullis Krum 73 SPNG_73 -- Unnamed -- -98.5252 29.7048 No nm nm -- Upper evaporite Krum 74 SPNG_74 -- Unnamed -- -98.5264 29.6948 No nm nm -- Camp Bullis Krum 

75 SPNG_75 -- Unnamed -- -98.5264 29.6942 No nm nm -- Camp Bullis Krum 

76 SPNG_76 -- Unnamed -- -98.5268 29.6942 No nm nm -- Camp Bullis Krum 77 SPNG_77 -- Unnamed -- -98.5811 29.679 No nm nm -- Fossiliferous Eckra

pe

78 SPNG_78 -- Unnamed -- -98.5815 29.6797 No nm nm -- Upper 

evaporite

Eckra

pe
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CoContinued[USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer]

Map 

identifier Unique identifier USGS station number Name of spring

Source 

of 

spring 

name

Longitude 

(dd)

Latitude 

(dd)

Field 

verified

Specific 

conductance 

(μS/cm at 

25 °C)

Discharge 

(ft3/s)

Field 

visit date (MM/DD/

YY)

Field 

observation 

at land 

surface

79 SPNG_79 -- Unnamed -- -98.5841 29.6747 No nm nm -- Camp Bullis Brack

20 

80 SPNG_80 -- Unnamed -- -98.5956 29.6624 No nm nm -- Upper 

evaporite

Eckra

pe

81 SPNG_81 -- Unnamed -- -98.6074 29.685 No nm nm -- Fossiliferous Eckra

pe

82 SPNG_82 -- Unnamed -- -98.6077 29.6833 No nm nm -- Fossiliferous Eckra

pe

83 SPNG_83 -- Unnamed -- -98.6157 29.6771 No nm nm -- Camp Bullis Brack

20 

84 SPNG_84 -- Unnamed -- -98.6182 29.677 No nm nm -- Cavernous Brack

20 

85 SPNG_85 -- Unnamed -- -98.6139 29.6779 No nm nm -- Camp Bullis Brack

20 

86 SPNG_86 -- Unnamed -- -98.6063 29.6694 No nm nm -- Camp Bullis Eckra

pe

87 SPNG_87 -- Unnamed -- -98.5925 29.6445 No nm nm -- Cavernous Brack

20 

88 SPNG_88 -- Unnamed -- -98.5919 29.6448 No nm nm -- Camp Bullis Brack

20 

89 SPNG_89 -- Unnamed -- -98.5773 29.6324 No nm nm -- Cavernous Eckra

15 

90 SPNG_90 -- Unnamed -- -98.5786 29.6296 No nm nm -- VIII1 Eckra

15 

91 SPNG_91 -- Unnamed -- -98.5431 29.6858 No nm nm -- Upper 

evaporite

Krum 

92 SPNG_92 -- Unnamed -- -98.5503 29.6729 No nm nm -- Camp Bullis Brack

12 

93 SPNG_93 -- Unnamed -- -98.5506 29.6663 No nm nm -- Camp Bullis Krum 

94 SPNG_94 -- Unnamed -- -98.5584 29.6673 No nm nm -- Camp Bullis Brack

12 

95 SPNG_95 -- Unnamed -- -98.559 29.6687 No nm nm -- Camp Bullis Brack

12 
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CoContinued [USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer] Map identi- fier Unique identifier USGS station number Name of spring Source of spring name Longitude (dd) Latitude (dd) Field verified Specific conduc- tance (μS/cm at 25 °C) Dis- charge (ft3/s) Field visit date (MM/DD/ YY) Field observation at land surface 

96 SPNG_96 -- Unnamed -- -98.5592 29.6688 No nm nm -- Cavernous Brack

to 

97 SPNG_97 -- Unnamed -- -98.5577 29.6417 No nm nm -- Cavernous Krum 98 SPNG_98 -- Unnamed -- -98.5254 29.6822 No nm nm -- Camp Bullis Eckra

pe

99 SPNG_99 -- Unnamed -- -98.5515 29.6506 No nm nm -- Cavernous Brack

20 

100 SPNG_100 -- Unnamed -- -98.5593 29.6427 No nm nm -- Cavernous Brack

12 

101 SPNG_101 -- Unnamed -- -98.5426 29.6853 No nm nm -- Upper evaporite Krum 

102 SPNG_102 -- Unnamed -- -98.5559 29.6783 No nm nm -- Cavernous Brack

12 

103 SPNG_103 293505098454101 6826602 TWDB -98.7615 29.5847 Yes nm nm 01/19/11 Cavernous Eckra

15 

104 SPNG_104 294227098413800 6819521 TWDB -98.694 29.7077 Yes 570 1.46 10/13/10 Middle Trinity Krum 

104 SPNG_104 294227098413800 6819521 TWDB -98.694 29.7077 Yes 671 nm 3/18/2011 Middle Trinity Krum 

105 SPNG_105 294228098415700 6819522 TWDB -98.6993 29.7079 Yes nm nm 10/04/10 Fossiliferous Brack

20 

106 SPNG_106 294225098412800 6819523 TWDB -98.6914 29.7071 Yes 1,130 0 03/18/11 Middle Trinity Eckra

pe

107 SPNG_107 294215098412200 6819524 TWDB -98.6895 29.7043 Yes nm nm 10/04/10 Middle Trinity Eckra

pe

108 SPNG_108 293819098401401 6819816 TWDB -98.6706 29.6386 Yes 854 0.106 10/20/10 Cavernous Krum 

108 SPNG_108 293819098401401 6819816 TWDB -98.6706 29.6386 Yes 954 0 8/19/2011 Cavernous Krum 

109 SPNG_109 293813098395801 6819924 TWDB -98.6662 29.6371 Yes 779 0.023 10/20/10 Cavernous Krum 

110 SPNG_110 293957098382201 6819925 TWDB -98.6396 29.6659 Yes 167 0 11/12/10 Camp Bullis Tinn 

slo

111 SPNG_111 294013098385901 6819647 TWDB -98.6499 29.6704 Yes 388 0 11/12/10 Middle 

Trinity

Tinn 

slo

112 SPNG_112 294043098400201 6819525 TWDB -98.6673 29.6786 Yes 450 nm 11/12/10 Middle 

Trinity

Patric

slo
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CoContinued[USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer]

Map 

identifier Unique identifier USGS station number Name of spring

Source 

of 

spring 

name

Longitude 

(dd)

Latitude 

(dd)

Field 

verified

Specific 

conductance 

(μS/cm at 

25 °C)

Discharge 

(ft3/s)

Field 

visit date (MM/DD/

YY)

Field 

observation 

at land 

surface

113 SPNG_113 293947098381501 6819910 TWDB -98.6374 29.6629 Yes 828 0.013 11/12/10 Cavernous Lewi

pe

113 SPNG_113 293947098381501 6819910 TWDB -98.6374 29.6629 Yes 828 0.008 8/19/2011 Cavernous Lewi

pe

114 SPNG_114 293537098411001 6827214 TWDB -98.6862 29.5938 Yes 490 0.110 11/02/10 Camp Bullis Tinn 

slo

115 SPNG_115 293627098410401 6827215 TWDB -98.6845 29.6076 Yes 568 0.250 11/22/10 Camp Bullis Tinn 

slo

115 SPNG_115 293627098410401 6827215 TWDB -98.6845 29.6076 Yes 698 nm 8/19/2011 Camp Bullis Tinn 

slo

116 SPNG_116 294056098323201 Panther 

Springs

GNIS -98.5423 29.6821 Yes 648 nm 11/29/10 Camp Bullis Krum 

117 SPNG_117 294217098464601 6818602 TWDB -98.7795 29.7047 Yes 598 0.005 12/01/10 Cavernous Brack

20 

118 SPNG_118 294408098413001 6819214 TWDB -98.6932 29.7353 Yes 506 0.595 12/02/10 Middle 

Trinity

Oaka

slo

119 SPNG_119 293942098402401 6819817 TWDB -98.6733 29.6617 Yes 463 0 12/09/10 Fossiliferous Brack

20 

120 SPNG_120 294318098453001 6818302 TWDB -98.7584 29.7218 Yes 624 0.433 12/08/10 Fossiliferous Krum 

slo

121 SPNG_121 294120098421902 6819526 TWDB -98.7054 29.689 Yes 608 nm 03/18/11 Middle 

Trinity

Lewi

pe

122 SPNG_122 294146098234902 6821602 TWDB -98.397 29.6963 Yes 741 0.007 04/05/11 VIII1 Eckra

15 

123 SPNG_123 294143098234602 6821608 TWDB -98.3961 29.6955 Yes nm 0 04/05/11 VIII1 Eckra

15 

124 SPNG_124 294143098233802 6821609 TWDB -98.3941 29.6954 Yes nm 0 04/05/11 Cavernous Eckra

15 

125 SPNG_125 293915098372602 6820720 TWDB -98.6241 29.6544 Yes nm 0 04/01/11 Fossiliferous Lewi

pe

126 SPNG_126 294310098440801 6819109 TWDB -98.7356 29.7194 Yes nm nm 04/01/11 Fossiliferous Oaka

slo

127 SPNG_127 293647098400201 Huesta 

Springs

GNIS -98.6667 29.6133 Yes 493 0.018 12/10/10 Cavernous Eckra

15 
Appendix 1. Geodatabase and characteristics of springs within and surrounding the upper and middle Trinity aquifer outcrops in northern Bexar CoContinued [USGS, U.S. Geological Survey; dd, decimal degrees; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ft3/s, cubic feet per second; MM/DD/YY, month/day/

Information System; TWDB, Texas Water Development Board; --, not applicable; nm, not measured. Green shading indicates informal hydrostratigraphic unit; gray shading indsubdivision; blue shading indicates aquifer] Map identi- fier Unique identifier USGS station number Name of spring Source of spring name Longitude (dd) Latitude (dd) Field verified Specific conduc- tance (μS/cm at 25 °C) Dis- charge (ft3/s) Field visit date (MM/DD/ YY) Field observation at land surface 

128 SPNG_128 -- Unnamed -- -98.4683 29.6706 No nm nm -- Cavernous Eckra

pe

129 SPNG_129 294048098235701 Walnut Spring GNIS -98.4001 29.6799 Yes 469 0 10/15/10 VIII1 Eckra

15 

130 SPNG_130 294059098240101 Cherry Spring GNIS -98.4007 29.683 No nm nm -- VIII1 Eckra

15 

131 SPNG_131 293912098453201 6818903 TWDB -98.7583 29.6542 Yes nm 0 09/07/11 Fossiliferous Krum 

132 SPNG_132 294020098453201 6818601 TWDB -98.759 29.6721 Yes nm 0 09/07/11 Fossiliferous Krum 

133 SPNG_133 293916098452801 6818604 TWDB -98.7583 29.6542 Yes nm 0 09/07/11 Fossiliferous Krum 

134 SPNG_134 294038098232401 6821606 TWDB -98.3903 29.6772 Yes nm 0 03/04/09 Cavernous Eckra

15 

135 SPNG_135 294105098263301 6821520 TWDB -98.4427 29.6849 Yes nm 0 03/18/11 Cavernous Craw

136 SPNG_136 294216098464601 6818603 TWDB -98.7795 29.7044 Yes nm 0 12/01/10 Cavernous Brack

20 

137 SPNG_137 294126098314702 6820610 TWDB -98.5303 29.6908 Yes nm 0 05/14/12 Upper evaporite Krum 

138 SPNG_138 294119098324502 6820511 TWDB -98.5462 29.6887 Yes nm 0 05/14/12 Camp Bullis Krum 

139 SPNG_139 294122098323502 6820512 TWDB -98.5432 29.6897 Yes nm 0 05/14/12 Camp Bullis Krum 

140 SPNG_140 294208098341602 6820513 TWDB -98.5715 29.7024 Yes nm 0 05/14/12 Fossiliferous Krum 

141 SPNG_141 294226098341702 6820514 TWDB -98.5719 29.7074 Yes nm 0 05/14/12 Fossiliferous Krum 

1Hydrogeologic subdivision VIII of the Edwards aquifer (Maclay and Small, 1986).
Publishing support provided by

Lafayette Publishing Service Center

Information regarding water resources in Texas is available at 

http://tx.usgs.gov/
 
Clark and others—Geodatabase and Characteristics of Springs Within and Surrounding the Trinity Aquifer Outcrops, 2010–11—DS 750